Method of making platinumcontaining catalysts



Patented Jan. 26, 1954 METHOD OF MAKING PLATINUM- CONTAINING CATALYSTS Walter R. F. Guyer, Roselle, John P. Thorn, Elizabeth, and Erving Arundale, Westfield, N. J assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application December 21, 1950, Serial No. 202,130

6 Claims.

This invention relates to the preparation of catalysts and more particularly relates to the preparation of platinum-containing catalysts.

Catalysts containing platinum have been described for various processes in the prior art but the commercial use of such catalysts has been limited because of the cost of platinum. Some time ago a hydroforming process utilizing platinum-containing catalysts was disclosed in U. S. Patents 2,479,109 and 2,479,110. These patents disclose a preferred method for the preparation of platinum-containing catalysts. We have developed a new method of making platinum containing catalysts which give vastly superior results in the hydroforming of naphthas. The patents referred to also disclose that hydrocracking is desired along with aromatizing reactions. We prefer to minimize the hydrocracking reaction which thereby results in a more selective process for producing aromatics. At lower pressures our process using the catalyst made according to our method reduces the amount of hydrocracking and increases the concentration of higher boiling aromatics in the naphtha or gasoline fraction being treated.

We have invented a new method of making platinum-containing catalysts which, when used for hydroforming naphthas or gasoline fractions,

' produce high yields of high octane number gasoline. Our catalyst is especially adapted for reforming light or heavy naphthas, straight run gasoline, cracked naphthas or mixtures thereof with the preceding feeds, selected naphtha fractions or mixtures thereof, in the presence of jgin naphthas contain naphthenes, paraflins and manner.

2 some aromatics. The hydroforming process dehydrogenates the naphthenes to aromatics and may also convert a portion of the parafiins to aromatics. Other reactions probably occur but the abovementioned reactions are the predominant ones.

By hydroforming is meant an operation conducted at elevated temperatures and pressures in the presence of a solid catalyst and added hydrogen for reforming naptha and gasoline fractions to increase the aromaticity thereof without any net consumption of hydrogen during the process. Since there is a net production of hydrogen during the process, the gas separated from the higher boiling products contains hydrogen which is recycled to the process and which provides the hydrogen-containing gas for the hydroforming operation.

According to the present invention the starting material for the catalyst is a crystalline activated alumina of commerce. The crystalline activated alumina is pulverized anddried and then treated with an aqueous solution of hydrogen fluoride until the hydrogen fluoride solution is substantially completely absorbed by the activated alumina. The mixture is allowed to stand for an extended period of time to permit reaction between the hydrogen fluoride and the activated alumina base. The mixture is then dried at a moderate temperature for an extended period of time. The dried mixture sunstantially at room temperature is granulated and then treated with a solution of a platinum compound such as chloroplatinic acid or the like until the solution is substantially completely absorbed by the treated activated alumina. Just sufficient water is added with the platinum-containing solution to form a paste and to permit dispersion of the platinum-containing compound throughout the alumina base in a homogeneous Hydrogen sulfide is then bubbled through or otherwise contacted with the paste and this pasty mixture is allowed to stand a short time and then dried at a moderate temperature. The resulting mixture is broken up into a powder and, if de sired, formed into pills. The catalyst in the desired form is then calcined at an elevated tern-- perature. the catalyst is reduced with hydrogen and is then ready for use in the hydroforming process. While in the above-described method of preparation of catalysts the activated alumina is HF treated and then the platinum is precipitated thereon, it is within the scope of this invention to soak the activated alumina with the platinumcontaining solution, precipitate the platinum and then HF treat the alumina containing the plati num.

A catalyst; prepared. according. to our method has higher activity and selectivity than catalysts prepared in accordance with the prior art. Qur specific method for preparing our catalyst will now be given.

Activated aluminas are well known in-the art and may be purchased. .in-.;;the. .open. market. Three crystalline activated aluminasfwhi ch of particular value in the preparation of ,-.our preferred catalyst are the following grades o Alorco alumina manufactured by. the Aluminum Company of America:

l Alorco grade nSuriace area mflg.

.Pore s zaAngstrp "Porosity; pergent' :rFWhile ive have set forth ,above several Ispeeifi-e crystalline activated. galuminas which'. ,we' have About. .690 gramspf fi l i meshF- m Alorco activated alumina were pulverized sonthat, about 80% of thematerial passed a;.-1 Io.-6 0 (U. S.) sieve, sand, the-pulverized aluminarwas dried at a .tem-

peratureof about 250 Fi overnight or-for about lfi hours. {The entire-batch oidried aluminawas n h ousllly'lllixeiefii' tq m em ia ure an aqueous solution of --hydrogen fluorid .pr epared by adding 12-grams of i8% aqueous hydrofiuoric acid. to .400 cc... of. distilled -.water) to form a paste. 'Theentire batch of alumina. and ,all of the solutionwveremixed{together.at once. The; HF solution was substantially. completely absorbed by, the alumina and the resulting mixture was thoroughly mixed -forabout hour at room temperature. By paste, wherever Preferably following the calcination,

mentioned herein, we mean a mixture of such consistency that only about 3-8% liquid of the total volume rises as a supernatant layer after standing for about 15 minutes to one half hour. The paste was permitted to stand at room temperature overnight or for about 16 hours to provide time for reaction between the alumina base and the hydrogen fluoride. This step is of considerable importance. The paste was then dried overnight or for about 16 hours at a temperature of about 250 F. The amount of HF used was about 1% by weight of the alumina.

The dried paste was broken up into a powder and then 75 grams of a aqueous solution of chloroplatinic acid, plus about 400 cc. of distilled water were added to the hydrogen fluoride treated alumina particles at room temperature and the entire batch was mixed for about minutes until; the alumina substantially:ncompletely ab sorbed the solution of chloroplatinic acid. In this way the solution of platinum compound impreg- --nates the alumina particles and a very homoge- ;;neous distri;bution of the platinum compound on "jtheial-umina particles is obtained. The amount of platinum on the HF treated alumina was i lystf, preparation in the two impregnating steps above described.

The; .paste-;of 'HF treated alumina base impregnated with the platinum compound was mixed .utesfluntillthe In 1 ub tanti andrduring mixing was treated with hydrogen sulfide gas by bubbling the hydrogen sulfide gas through the paste for about 1 /2 hours at a moderate rate to depositor-preeipitate the platinum in fsitu' "on the alumina particles. i The" sulfided pasty mixture was then'allowed-tostand for about 4 hours at room'tem'perature' and was-then put in a cold drying-oven. The temperature" ofthe oven-was then raised and the=--paste was dried overnight or about 16 hours-fat about 250" F.

The dried sulfided mixture was then broken up into a powder:Whichgwasp'illed" -withouta a binder into cylindrical pills havinga size of about 9e" by 'z e'. The pills were' caleined at about 950 F. for about two hours. After calciningythe pills I atabout room temperature -were treated or reducedawith hydrogen as the: catalyst was slowly broughtmp to 900 i-F.. overnight' or about 16 hours at. atmosphericipressure ithat is, the- 'temperature was raised175ito "-'F. perihour. :The amount of:hydrogenpassed overithe catalyst was about: 1 00 1 volumes of: ahydrogenla-per .-;-volume fof catalyst per hounyvithat leastrhalf:theitreatment or about: 8 hours -occurlringi at? 800. 900. F.

600 grams of -i? ,Fme, 1 fHf-;41' 'A1QI'QQ activated alumina:- wereipulver i zed; and .thepulverized-alumina was .drijedsat-aetemperature oi about- 2 503-1 overnight; or.- for about -1 h ou rs. .1 The .entire 11 mm we -t en t u h mixedr -at room; emperatureswith an-eaqueous solution-of h-ycliQg n fiuoride prepared by. .adding 6 grams of- 4 8% .a ueous hydrofiuoricacidto 500 cc.,.oi .distilledyrat'erl J90. iormlapaste. lfThe paste was mixed, al en. alloweditostandat room temperature-and. dried'gas Examp1e] .1. T'I Ihe .dried paste was. brokenup, into-a powder. and".75 grams of. an.aqueous..1.0 sol'ution of. chloropla- .tinic;acid p1us--about5.(l0cc. piifdistilled waterwere ad 12 il lH treated al m na. .p t e a room. temperature and mixed iorabout 15min- ';i ;bmp e el absorbed the 'chloroplatinic' 'cid solution. The

catalyst was then finished in the same manner given in Example 1. The catalyst contained 0.5% by weight of platinum and 0.5% by weight I of HF.

The above examples give specific details for the production of an improved catalyst according to our invention and while certain of the steps are essential for producing our improved catalyst, such as drying the alumina, contacting the dried alumina with HF and allowing to stand, drying the HF treated alumina, adding the platinum solution to form a paste, treating the paste with HzS, drying, calcining and reducing; certain of the conditions may be varied and need not be exactly restricted to those given in the examples. For example, drying of the ground activated alumina may be at 212 F. to 950 F. for 2 to 24 hours, the shorter times being used at the higher temperatures. The mixing of the aqueous HF solution and dried, ground activated alumina may be continued for about ten minutes to about one hour, while adding water, if necessary, to maintain a pasty condition of the mixture but excessive water addition is to be avoided. The paste may be allowed to stand at room temperature from about 2 hours to 24 hours to allow time for the reaction between the hydrogen fiuoride and alumina base. The paste may then be slowly dried at a temperature of about 212 F. to 400 F. for about 8 hours to 24 hours, the shorter times applying to the higher temperatures. After the addition of the chloroplatinic acid solution to the HF treated and dried alumina to form a paste, the mixing may continue for 5 minutes to one hour at room temperature. It is also possible to add the HF to the chloroplatinic acid solution and then add the resulting mixture to the dried alumina. The HF treated alumina containing the platinum compound is then treated at room temperature with.

ried out, if desired, under superatmospheric presa sures. This permits the use of shorter treating times. As another alternative the HF treated activated alumina may be put under subatmospheric pressure to degas the alumina by evacuation and then treated with the platinum-con-.

taining solution to obtain improved impregnation of the alumina with the platinum. After stopping the addition of H23 gas, the mixture may be allowed to stand minutes to 24 hours at room temperature. The sulfided mixture may then be dried at about 212 F. to 400 F. for about 2 hours to 24 hours, the shorter times being employed at the higher temperatures. The catalyst, in pilled or powdered form, may be calcined at 800 F. to 1000 F. for about 1 hour to 8 hours, and then reduced with hydrogen by pasing 50 v./v./hr, (volume of hydrogen per volume of catalyst per hour) to 12,000 v./v./hr. of hydrogen at about 700 F. to 1000 F. for about 2 hours to 12 hours. In this hydrogen treatment the treated alumina pills are slowly raised to the final temperature, as above described, preferably starting at room temperature.

For preparing catalysts containing larger amounts of platinum, larger amounts of chloroplatinic acid are used and for catalysts containing more or less fluorine different amounts of HF may be used. Gaseous HF may be used but aqueous solutions of HF are preferred. Instead at using fluorine compounds other halogens such as hydrochloric acid may be used but the fluorine containing substances are preferred.

The amount of platinum in the finished catalyst is preferably between about 0.1% and 1.0% by weight but in some cases may be as high as 2.0%. The amount of HF used may vary from about 25% to 3% by weight of the catalyst with about-0.5% to' 1% HF preferred. The H-41 aluminas will generally require smaller HF treats than the F-10 aluminas to produce equivalent results. For example, catalysts prepared from 11-41 alumina possess optimum activity when containing about 0.5% HF, whereas those prepared from the pure aluminas (e. g. F-10) possess optimum activity when containing about 1% HF. In general, the use of' higher amounts of HF, for the same set of operating conditions, will result in a more active catalyst giving more volatile gasolines (higher Reid vapor pressure) but lower octane number products so that HF treats in the range above given are to be preferred.

For hydroforming operations using our new platinum-containing catalyst the temperature may be between about 600 F. and 1000 F., preferably 800 F. to 950 F., the pressure, atmospheric to about 1000 lbs per square inch, the naphtha feed rate about 0.25 to 4 v./v./hr. (volume of liquid feed per volume of catalyst per hour) preferably 1 to 2 v./v./hr. in a fixed bed unit and the hydrogen-containing recycle gas is recycled at the rate of about 2,000 to 12,000, preferably 6,000 cubic feet per barrelof feed. In the hydroforming process the recycle gas contains about 80 to 99% hydrogen by volume. In general, higher feed rates produce essentially the same yield of gasoline but the octane number and volatility are reduced appreciably.

The platinum-containing catalysts prepared by the above-described specific method when used in hydroforming give improved results at high pressures from about 500-1000 lbs. per square inch but they are even more effective at low pressures of the order of 50 to about 250 lbs. per square inch.

Catalysts of the same nominal composition as described above can be made by other methods. However, as will be seen by the following example, the catalysts prepared according to the method of the present invention possess superior activity and selectivity in the hydroforming of naphthas.

Example 3 alysts prepared as described in Examples 1 and 2 above as well as in the presence of two other catalysts to be described hereinafter in connection with the last two columns in the table.

These catalysts were used in pill form as a "fixed bed which was heated to a temperature of about 900 F. The heating was done by an electric coil wound around the reactor. The feed rate was about 1.2 v./v./hr. and the amount of hydrogen gas used was about 6,000 cubic feet per barrel of naphtha feed. The following table summarizes the data obtained when using these catalysts.

i TABLE, I

catalyst eompositionz- P9rcentpletinumiweightiauu----- .--s v .5

PercentHFtreated'alumina 99 alumina gel PercentfiFfonalmninaiadded) .o 12.- Percent-Yfluorineonalumina-(byanalys 0. Reaction conditions:

' 90'; Pressure p. s. 750 650. Feed rate,*v./v 1:21. 1.10. fiz 'flydnbcarbonmo at 6.0. 6.;7 Gasoline-% Uri-basis:

Yield, yolume'percent 98. 8 83;0- Rsearchoctane mum 80.1.0 76 8 0 Reid vaponpressure" 15.3 16.7 'GasolineO +basis:

Researchocmnemumbemmlear 14. .4 7L8 Reidzvaponpressure 4.8 8.4

B As described in Examplel. As described in'E xamplez;

@ Each Hi/HGzmol ratio:isabout equiva'ient to lflflfl emit-of hydrogenper barrel of naphtha feed. 4 is per Example 1but-with'2%'HF.

was pert Example -2 but wlth 2% Theeatalyst was preparedlasfollows Diluted ammoniumhydroxidew-as added to analuminum chloride solution: Withstirr1n'g,- the final-;pH -bein g adgusted to about 9.5. After filtering the aluminum hydroxide precipitate and back'washing in a filter press, the precipitate was re-s1urried,= filtered and hank-wasliedforfiveadditional times. Thirty-two kilograms of wet cake were preparedm this manner, having an ignition 1oss=of'-90-;4%=at 1000 11. ThisFgel was treated with" a solution of gl000'cc. of water plus 128 grained/18% aqueous-HF, and was thoroughly mulled inn-*Lancastermixer fo'r one hour, so thatlan HF portion of thisHF. treated .aluminaigel corresponding to "From the data. given in the above table; it will be seen that, under comparable operating "conditions catalysts. prepared according, to the method of this invention permiti the production o'f"'gasolines of higher octane number-Sthanran he obtained with catalystsoffthe same nominal composition prepared "by other means.

While the specific examples above-given show results obtained. in a hydroforming' operation using thecat'aIySt as a fixed bed, it is to be understoodthatlour. improvedcatalyst may be 'usedin pill'or beadform'inamoving bed'operation .wheretlie catalyst moves down as a "compact mass through a .reactor or th'etatalystmay be ground andlused in powdered'form where'the catalyst'is maintainedas a dense'ifiuidi'zedturbulent bed in a reactor by the up'flo'wing reaction gases. When usin'gga'fiui'djprocessthe crystalline alumina is groun'dto theproper size sothat after the cat'alyst'ismade by the above metho'dit Will he of the'prop'er s'ize'for-the'fiuidprocess.

There is "a net production of" hydrogenduring the 'liydroiorming process carried out with our ing'the hydrogen (800042000 v./v'./hr.)- over the-catalyst to remove the carbonaceous material. When -using:HF treated catalysts, air may be used to regenerate the catalyst butin such cases it may be necessary to treat the catalyst; r'H-E- following the regeneration treatment or during regeneration treatment.

.an. elevatedtemperature andthentreating the provide about 0.1 to 2.0% by weight of platinum a sufficient amount; of aqueonssoi 39.0 ;grams,of aluminamwas dfiedfovei-night at 250"'F., calcinedfor 2 hours at-925' F-J and thenpulvemzdiin-:8. vBraunpulvenizer. A .solutionqof 50-.8;;g1 :ams;of 10 %-,chloroplatiniceacid lus 280..cc. of water was mixed verylthor- 'ou'ghly With-t 'etreatellalumina gel particlesp This'm-a'terialwas:.tI:eated ,with hydrogen sulfideiandtheneilried over- 11 1-51134. After-drying overnightat 250? E. the catalystwas pr e 7 iThisycatalystiwas gprepared gin 'the'r following manner A,so1 ut1on.o aluminum chloride was stirred into dilute amnromummydromda-the final pH being adjusted-to about .elQ; Theiprecipitate was washed andfreslurriedrthree;times wlthudiluteeammoniuml hydroxide .(pH,=10-) Thewashed 'cakewvas treated 'with 2% HF by weight; based on-the aluminzncontentnnd mixed'with asluri'y'made by-bubblin hydrogen sulfide through .adilute. chloroplatinicacid solutIon. Att'er drying at 250"F.andcalciningior"El-hours at 9:00. Eiithe oatalyst waspilled.

Whatfis-claimedis;

Process,- of manufacturing .platinum containing reforming. catalysts which. comprises -a crystalline-activated alumina -.with

an aqueous.- l-IF solution, to forma pasteausing sufiicientsoiutiomto bathe equivalentiof 0.25% to 3.0% ofml-iF 'ontalumina bywei-ght, mixing the paste and then permitting ,the mixture to stand'z'at room temperature to permit, reaction between thealuminaand the-HF, drying thewpaste and .then' mixing ltuWlth a zsolutionofr a platinum compound to; form a paste sa-id amount of solution beinasufiicient :to provide 1 abouti 0.1;.to 250% by weight of platinum on the alumina; :then treating-the paste withHLeS for anextended pecried of time to-uniiormlydeposit the platinum .on-the alumina'base permitting the sulfided "mixture'fto stand ataroom temperature for an extended period oftime sufiicient to allowthe desired reaction, then dryingthesulfided mixture. and afterdrying calcining, the mixture-at calcined. mixture with hydrogen. to reducethe ,platinumto the metallic state.

.2; Process of manufacturing -platinum-eontaining reforming catalystswhichcomprises mixing .a 'dry' crystalline activated.-aluminaWwith an aqueous solution containing. activating amounts of. fluorine and-usin'gwnly asufiicient amount of theso'lution so thatlit is substantially completely absorbed 1 by the alumina tov form, a =paste=using sufiicientsolutiento he the equiva- 4lent of"0.25% to 3.9%. of HF on-aluminaby weight permitting the pastyvm-ixture to, stand to-allow time for reaction between the, fluorine containing solution and the alumina, drying the 'fluorine.- treated alumina and'then mixing iii-with OHIIOf; a platinum compound-suchthat the-solution; is substantially completely absorbed-by the alummasaid amount of solutiombeingsuflioient to onthealumina, treatingthemiXture With- H28; to

precipitate platinum on -the alumina homogeneous manner,- calcining the, res and-then treatingthecamined mix .ure. eta-810 ing mixture ly rising temperature with hydrogen to reduce the platinum to the metallic state.

3. Process for making platinum-containing reforming catalysts which comprises drying solid particles of a crystalline activated alumina, mixing the dried alumina particles with an aqueous solution carrying an activating amount of a fluorine containing substance to form-a paste using sufficient solution to be the equivalent of 0.25% to 3.0% of HF on alumina by weight with the alumina substantially completely absorbing the solution, permitting the paste to stand to allow reaction between the alumina particles and the fluorine containing substance, heating the resulting paste to dryness, mixing a water solution of a platinum compound with the dried treated alumina particles at room temperature to form a paste said amount of solution being suflicient to provide about 0.1 to 2.0% by weight of platinum on the alumina, treating the paste with hydrogen sulfide to react with the platinum compound and permitting the sulfided mixture to stand at room temperature for a surficient period of time to permit the platinum to be laid down in a homogeneous manner on the alumina particles, drying the sulfided mixture, then calcining the dried sulfided mixture and thereafter treating the calcined mixture with hydrogen to reduce the platinum to the metallic state.

4. A process of making platinum-containing reforming catalysts which comprises mixing dry crystalline activated alumina particles with an aqueous solution of HF to form a paste and having sufficient HF present in an amount equivalent to about 1% HF on the alumina by weight, permitting the mixture to stand at room temperature to allow reaction between the alumina particles and the HF, heating the paste to dryness, mixing a solution of a platinum compound with the dried HF-treated alumina particles at room temperature to form a paste and using suflicient amount of the platinum compound to have about 0.5% of platinum by weight of the alumina in the final catalyst, treating the resulting paste with hydrogen sulfide, permitting the sulfided mixture to stand for a sufficient period of time to permit the desired reaction and to homogeneously deposit platinum on the particles of treated alumina particles, drying the sulfided mixture, then calcining the dried sulfided mixture and thereafter treating the said mixture with hydrogen to reduce the platinum to the metallic state.

5. A process for making platinum-containing reforming catalysts which comprises drying solid particles of a crystalline activated alumina, mixing the dried activated alumina particles with an aqueous solution of HF to form a paste and using suflicient HF to be the equivalent of 0.25% to 3% of HF on alumina by weight, mixing the resulting paste for about half an hour at room temperature and then permitting the mixture to stand at room temperature for an extended period to provide time for reaction between the alumina particles and the HF, drying the HF treated alumina particles for an extended period at a temperature of about 250 F., mixing the resulting dried alumina particles with a platinum-containing solution sufficient to provide about 0.1 to 2% by weight of platinum on the alumina, passing hydrogen sulfide through the mixture of alumina particles containing the platinum compound to deposit the platinum on the alumina particles, drying the sulfided mixture for an extended period at about 250 F., calcining the dried sulfided particles at a temperature between about 800 F. and 1000 F. for about 2 hours and then reducing the catalyst with hydrogen by passing hydrogen over the catalyst for an extended period with a slowly rising temperature with the final temperature being between about 900 F. and 1000 F. to reduce the platinum to the metallic state.

6. A process for making platinum-containing reforming catalysts which comprises drying solid particles of crystalline activated alumina, mixing the dried alumina particles with an aqueous solution of HF to form a paste and using sulficient HF to be the equivalent of about 0.5 to 1% HF on alumina by weight, mixing the resulting paste for about half an hour at room tempera-' ture and then permitting the mixture to stand at room temperature for an extended period to provide time for reaction between the alumina particles and the HF, drying the HF-treated alumina particles for an extended period at a temperature of about 250 F., mixing the resulting dried alumina particles with a platinum-containing solution sufficient to form a paste and to provide about 0.5% by weight of platinum on the alumina, passing hydrogen sulfide gas through the paste of alumina particles containing the platinum compound to homogeneously deposit the platinum on the alumina particles, drying the sulfided mixture for an extended period at about 250 F., calcining the dried sulfided particles at a temperature between about 900 F. and 950 F. for about 2 hours and then reducing the catalyst with hydrogen by passing hydrogen over the catalyst for an extended period with a slowly rising temperature and the final temperature being between about 900 and 950 F. whereby substantially all of the platinum is reduced to the metallic states.

WALTER R. F. GUYER.

JOHN P. THORN.

ERVING ARUNDALE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,348,624 Hillman May 9, 1944 2,381,562 Stewart Aug. 7, 1945 2,426,118 Parker et a1 Aug.,19, 1947 2,478,916 Haensel et al Aug. 16, 1949 2,479,109 Haensel Aug. 16, 1949 2,606,878 Haensel Aug. 12, 1952 

1. PROCESS OF MANUFACTURING PLATINUM-CONTAINING REFORMING CATALYSTS WHICH COMPRISES MIXING A CRYSTALLINE "ACTIVATED ALUMINA" WITH AN AQUEOUS HF SOLUTION TO FROM A PASTE USING SUFFICIENT SOLUTION TO BE THE EQUIVALENT OF 0.25% TO 3.0% OF HF ON ALUMINA BY WEIGHT, MIXING THE PASTE AND THEN PERMITTING THE MIXTURE TO STAND AT ROOM TEMPERATURE TO PERMIT REACTION BETWEEN THE ALUMINA AND THE HF, DRYING THE PASTE AND THEN MIXING IT WITH A SOLUTION OF A PLATINUM COMPOUND TO FORM A PASTE SAID AMOUNT OF SOLUTION BEING SUFFICIENT TO PROVIDE ABOUT 0.1 TO 2.0% BY WEIGHT OF PLATINUM ON THE ALUMINA, THEN TREATING THE PASTE WITH H2S FOR AN EXTENDED PERIOD OF TIME TO UNIFORMLY DEPOSIT THE PLATINUM ON THE ALUMINA BASE, PERMITTING THE SULFIDED MIXTURE TO STAND AT ROOM TEMPERATURE FOR AN EXTEDNED PERIOD OF TIME SUFFICIENT TO ALLOW THE DESIRED REACTION, THEN DRYING, THE SULFIDE MIXTURE AND AFTER DRYING, CALCINING THE MIXTURE AT AN ELEVATED TEMPERATURE AND THEN TREATING THE CALCINED MIXTURE WITH HYDROGEN TO REDUCE THE PLATINUM TO THE METALLIC STATE. 